1. Field of the Invention
The present invention relates to a toner supply device useable in an image forming apparatus such as a copier, a facsimile machine, and a printer, and an image forming apparatus including the toner supply device.
2. Description of the Background
Image forming apparatuses are used as copiers, printers, facsimile machines, and multi-functional devices combining several of the foregoing capabilities. A conventional image forming apparatus includes a detachably mountable toner supply device to supply toner to a developing device. When the toner supply device is mounted in or detached from the image forming apparatus with an opening provided in the toner supply device to discharge toner uncovered, a portion of the toner may be scattered from the opening, resulting in failures such as contamination of the image forming apparatus and/or its surrounding area. To prevent such scattering of toner, a shutter for alternately uncovering and covering the opening may be provided in the image forming apparatus. In such configuration, for example, the opening is uncovered by the shutter when the toner supply device is mounted in the image forming apparatus but covered with the shutter when the toner supply device is detached from the image forming apparatus.
A conventional toner supply device includes a shutter on a bottom wall of the toner supply device to discharge toner, movable between a closed position to close the toner discharge port and an open position to open the toner discharge port. The shutter is moved along an outer face of the bottom wall of the toner supply device by a guide member provided on the outer face of the bottom wall behind the toner discharge port with respect to the shutter. A seal member contactable against the outer face of the bottom wall is attached to the shutter so as to seal the toner discharge port when the shutter is at the closed position to close the toner discharge port. Such contact between the seal member and the outer face of the bottom wall can prevent a gap from forming between the shutter and the outer face of the bottom wall of the toner supply device, thereby providing excellent sealability.
FIG. 19 is a schematic view illustrating a toner transfer portion from a toner supply device 100 to a developing device 200 in an image forming apparatus. In FIG. 19, an opening 109 into which a shutter 125 is inserted is formed on a side wall of a case 101 that forms a part of a toner flow path t1. The shutter 125 is inserted as illustrated in FIG. 20 to open and close the toner flow path t1.
In this regard, the shutter 125 needs to reliably close the toner flow path t2 and fit snugly in the opening 109.
FIGS. 21 and 22 illustrate sectional views cut along a line XXI-XXI of FIG. 20. As illustrated in FIG. 21, if there are gaps 401 and 402 between the shutter 125 and the opening 109, toner may be inadvertently scattered from such gaps 401 and 402. Such toner scattering may occur, in particular, during operation of the image forming apparatus. For example, as illustrated in FIG. 20, during operation of the image forming apparatus, toner whose fluidity is increased by an agitator flows down from an upper portion of the toner flow path t1. As a result, a portion of the toner may be scattered through the gaps 401 and 402 to the outside of the case 101. Further, at a lower portion of the toner flow path t1 close to the developing device 200, a screw 204 for transporting the toner in a direction indicated by an arrow t2 in FIG. 20 flips the toner upward in directions indicated by arrows t3. As a result, a portion of the toner may be scattered from the gaps 401 and 402. When a toner having a relatively small particle diameter is used, such toner may more readily pass through the gaps to the outside, thereby resulting in more notable toner scattering. Alternatively, using a relatively high-speed developing device may cause the screw to flip up the toner intensively, similarly resulting in more notable toner scattering.
To prevent toner from being scattered from the opening 109, such gaps need be filled by closely contacting the shutter 125 against side surfaces 403 and 404 as illustrated in FIG. 22.
However, the shutter 125 and the side surfaces 403 and 404 may have dimensional tolerances, resulting in a discrepancy in size, and thus a discrepancy in fit, between the shutter 125 and the opening 109. In such a case, if the shutter 125 is too large compared to the opening 109, the shutter 125 may be prevented from moving into the opening 109, or moved only with great difficulty, thereby degrading the slidability of the opening 109. By contrast, if the shutter 125 is too small compared to the opening 109, gaps may appear between the shutter 125 and the side surfaces 403 and 404, resulting in toner leakage from the gaps.
Hence, in the above-described conventional toner supply device, the toner discharge port is provided to the outer face of the bottom wall of the toner supply device and the seal member is attached to the shutter so as to contact the outer face of the bottom wall of the toner supply device to prevent gaps from appearing between the shutter and the outer face of the bottom wall of the toner supply device.
However, in the conventional toner supply device, sufficient consideration is not given to gaps appearing between a guide member and end portions in the width direction of the shutter, which may result in toner leakage from the gaps.
In view of the above-described situation, the present disclosure provides a toner supply device capable of reliably opening and closing a shutter member to prevent toner from being scattered from the device, and an image forming apparatus including the toner supply device.